Bubble stick



FIG. 1 is a top perspective view of the bubble stick showing our new design;

FIG. 2 is a front elevation view of the bubble stick on a slightly reduced scale relative to FIG. 1, the opposing back view being identical;

FIG. 3 is a side elevation view thereof, the opposing side view being identical;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a bottom plan view thereof.

The broken lines showing interior structure are for illustrative purposes and form no part of the claimed design. 

The ornamental design for a bubble stick, as shown and described. 